The present invention relates to semi-conductor component modules, and is particularly but not exclusively applicable to rectifier or thyristor modules.
It is known to provide packages or modules containing a pair of semi-conductor rectifying or thyristor elements connected in series on a base from which these are electrically isolated. External contacts are provided on the package to enable electrical connection to all three terminals of the series connection of two elements.
Two such packages may be externally connected together to form a full wave rectifying bridge, and similarly three such packages may be interconnected to form a three phase rectifying arrangement.
Such modules or packages are commercially available in various standard sizes and also the spacing between the external terminals has become standardized. However, unfortunately, different manufacturers adopt differing sizes and standards. Thus, manufacturers of such packages or modules are presently forced either to offer two completely separate ranges of module or must concentrate on only a single range. Both options are commercially disadvantageous.
To be more specific, one known standard thyristor module of 130A nominal rating has an overall height of 30 mm and a terminal spacing of 23 mm. A second known equivalent standard module has an overall height of 41 mm and a terminal spacing of 25 mm.
When a plurality of modules of the first standard are connected together by heavy duty copper rods or the like, it is difficult if not impossible to replace a single module by another of the other standard even though its electrical properties may be perfectly adequate. Problems arise owing to the difference in height and the difference in terminal spacing.
According to one aspect of the invention, there is provided a semi-conductor element module having at least two external terminals, the distance between said terminals being adjustable
Another problem is concerned with the internal assembly method adopted for the modules. The semiconductor elements within the module may be electrically connected to terminals and other components either by means of soldering or by means of compression bonding. It will be appreciated that whichever method is adopted it is necessary in high power applications for these interconnections to pass a relatively large current without appreciable voltage drop, whilst maintaining the housing and junction temperatures within certain limits.
Both methods of connection have their advantages and disadvantages. Whilst a soldered assembly requires fewer components, produces better thermal characteristics and simplifies the housing, as well as rendering the production of a lower assembly more easy, it has disadvantages in that the terminals will be more complex, furnace operations are required, thermal expansion and mis-match can be expected and there are various problems with loss of yield. The selection of solder assembly is not accepted as readily by customers as is the compression bonded product.
It will be appreciated from the above that manufacturers generally prefer to adopt the compression bonded technique when this is feasible having regard to dimensional constraints of the finished package.
However it has previously proved impossible to provide a satisfactory compression assembled product of relatively low overall height.
According to a further aspect of the invention, there is provided a semi-conductor element module having a housing containing at least one semi-conductor junction having electrodes electrically connected to respective terminals by compression assembly, the semiconductor junction and terminals forming elements of a stack contained in the housing and further comprising at least one strain buffer, at least one electrical isolation member, and at least one electrically insulating compression member, compression forces being applied to the stack by at least one spring means, the height of said stack being less than 15 mm and the module being such that, in use with rated current, the junction temperature is no greater than 130.degree. C. and the housing temperature is no less than 80.degree. C.
Preferably, the spring means comprises a leaf or plate spring member.
Preferably, the each isolation member consists of alumina oxide or aluminium nitride.
Preferably, the compression member consists of ceramic, e.g. aluminium oxide, or mica.
The leaf or plate spring mentioned above is preferably of lozenge shape to even out the stresses applied to the spring element.
Preferably, the strain buffer is of molybdenum, tungsten or copper.